1. Field of the Invention
The present invention relates to catamaran air cushion ships. More particularly, the present invention relates to an improved surface effect ship or air cushion ship with a catamaran hull that enables low, high and intermediate speeds with improved efficiency.
2. General Background of the Invention
The typical side hull geometry that has been employed by surface effect ships is a prismatic, hard-chine planing hull. These types of hulls are inefficient at developing lift and have very high wave making drag characteristics when the ship is off cushion in the displacement mode. Their primary advantages come from their ease of production and their tendency to introduce a degree of dynamic stability at high speeds. In some situations, an intermediate speed that is in between a low displacement mode and a high speed air cushion mode is desirable.
In general, catamaran air cushion ships, also known as surface effect ships, are known. Examples disclosed in U.S. Patents are listed in the following table. The following table also lists some propeller related art.
TABLE 1IssueU.S. Pat. No.TitleDate1,976,046WaterfoilOct. 9, 19342,405,115Floating StructureAug. 6, 19463,065,723Supercavitating HydrofoilsNov. 27, 19623,077,173Base Ventilated HydrofoilFeb. 12, 19633,141,436Hydrofoil Assisted AirJul. 21, 1964Cushion Boat3,458,007Captured Air Bubble (CAB)Jul. 29, 1969Ground Effect Machine3,621,932Gas-Cushion VehiclesNov. 23, 19713,917,022Twin Cushion Surface EffectNov. 4, 1975Vehicle3,987,865Gas-Cushion Vehicle SkirtOct. 26, 19764,469,334Sealing System For The AirSep. 4, 1984Cushion Of An Air-CushionVessel4,489,667Surface Effect Ship SealsDec. 25, 19844,506,618Propeller And KeelMar. 26, 1985Arrangement For SurfaceEffect Ships4,535,712Variable Air Cushion ModeAug. 20, 1985Vehicle4,543,901Surface Effect Ship AirOct. 1, 1985Cushion Seal System4,646,866Surface Effect Type, SideMar. 3, 1987Keel Vessel Fitted With AnImproved Forward BuoyancyCushion Seal Apparatus4,660,492Catamaran Air Cushion WaterApr. 28, 1987Vehicle4,708,077Hull Shapes For SurfaceNov. 24, 1987Effect Ship With Side WallsAnd Two Modes OfOperation4,714,041Structure of surface effectDec. 22, 1987ship with side walls4,739,719Movable bow seal air rideApr. 26, 1988boat hull4,767,367Integrated CombinationAug. 30, 1988Propeller Drive ShaftFairing and Water IntakeSea Chest Arrangement, ForHigh Speed Operating MarineCraft5,651,327Displacement, SubmergedJul. 29, 1997Displacement, Air CushionHydrofoil Ferry Boat5,711,494Aero-HydrogliderJan. 27, 19985,934,215Stabilized Air CushionedAug. 10, 1999Marine Vehicle6,293,216Surface Effect Ship (SES)Sep. 25, 2001Hull Configuration HavingImproved High SpeedPerformance and HandlingCharacteristics6,439,148Low-Drag, High-Speed ShipAug. 27, 20026,526,903High speed M-shaped boat hullMar. 04, 20036,609,472Stable efficient airAug. 26, 2003lubricated ship2003/0000440Air Assisted Landing CraftJan. 02, 2003
Incorporated herein by reference are U.S. Pat. Nos. 4,767,367; 6,293,216; and 6,439,148. These three patents relate generally to surface effect ships or hovercraft.
Also incorporated by reference is the following:
JOHN LEWTHWAITE, “The PACSCAT Concept and its application to Fast Landing Craft”, presented at MACC Multi Agency Craft Conference 2002, The Pulse of Technology, 18–20 Jun. 2002, Naval Amphibious Base Little Creek, Norfolk (19 pages)